U.S. patent application number 13/930531 was filed with the patent office on 2014-01-02 for printed circuit board for rf connector mounting.
This patent application is currently assigned to Amphenol Corporation. The applicant listed for this patent is Prescott B. Atkinson, Marc B. Cartier, JR., Thomas S. Cohen, Mark W. Gailus, David Manter, Philip T. Stokoe. Invention is credited to Prescott B. Atkinson, Marc B. Cartier, JR., Thomas S. Cohen, Mark W. Gailus, David Manter, Philip T. Stokoe.
Application Number | 20140004724 13/930531 |
Document ID | / |
Family ID | 49778571 |
Filed Date | 2014-01-02 |
United States Patent
Application |
20140004724 |
Kind Code |
A1 |
Cartier, JR.; Marc B. ; et
al. |
January 2, 2014 |
PRINTED CIRCUIT BOARD FOR RF CONNECTOR MOUNTING
Abstract
An RF connector module and associated printed circuit board
providing high isolation and controlled impedance at RF
frequencies. The connector module may be manufactured using
conventional manufacturing techniques, such as stamping, insert
molding, multi-shot molding and interference fit between
components, to provide low cost. A connector module constructed
with these techniques may implement a co-planar waveguide
structure, with conductive shields for isolation and lossy material
to enforce co-planar propagation modes. The printed circuit board
may similarly be manufactured using conventional manufacturing
techniques, including drilling to form vias. As a result, an
interconnection system may be manufactured with low cost. These
techniques may be applied to provide performance, including in the
form of isolation between RF signals, comparable to that provided
by more expensive components.
Inventors: |
Cartier, JR.; Marc B.;
(Dover, NH) ; Manter; David; (Windham, NH)
; Atkinson; Prescott B.; (Nottingham, NH) ;
Stokoe; Philip T.; (Attleboro, MA) ; Cohen; Thomas
S.; (New Boston, NH) ; Gailus; Mark W.;
(Concord, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cartier, JR.; Marc B.
Manter; David
Atkinson; Prescott B.
Stokoe; Philip T.
Cohen; Thomas S.
Gailus; Mark W. |
Dover
Windham
Nottingham
Attleboro
New Boston
Concord |
NH
NH
NH
MA
NH
MA |
US
US
US
US
US
US |
|
|
Assignee: |
Amphenol Corporation
Wallingford Center
CT
|
Family ID: |
49778571 |
Appl. No.: |
13/930531 |
Filed: |
June 28, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61666674 |
Jun 29, 2012 |
|
|
|
Current U.S.
Class: |
439/65 |
Current CPC
Class: |
Y10T 29/49121 20150115;
H01R 12/712 20130101; H05K 1/0251 20130101; H01R 43/20 20130101;
H01R 12/7082 20130101; H01R 13/6587 20130101; H05K 1/0222 20130101;
H05K 1/024 20130101; H05K 2201/09063 20130101 |
Class at
Publication: |
439/65 |
International
Class: |
H01R 12/70 20060101
H01R012/70 |
Claims
1. A printed circuit board comprising a footprint for an RF
connector module, the printed circuit board comprising: a matrix
comprising material of a first dielectric constant; a signal trace
supported by the matrix; a conductive structure, parallel to and
isolated from the signal trace by the matrix; a first via connected
to the signal trace within the printed circuit board; a plurality
of second vias electrically coupled through the conductive
structure, the plurality of second vias being disposed around the
first via; a plurality of third vias, the third vias being disposed
in a region of the printed circuit board between the first via and
the plurality of second vias, the third vias have a second
dielectric constant different than the first dielectric
constant.
2. The printed circuit board of claim 1, wherein the plurality of
second vias are spaced the same distance from the first via.
3. The printed circuit board of claim 2, further comprising a
plurality of micro vias disposed in first column and a second
column, parallel to the first column, the first column and the
second column being on opposing sides of the first via.
4. The printed circuit board of claim 3, wherein: the printed
circuit board comprises a first signal launch region comprised of:
the signal trace; the first via; the plurality of second vias; and
the plurality of third vias; and the printed circuit board further
comprises a second, like signal launch region, wherein the first
via of the second signal launch region is disposed between the
first column and the second column.
5. The printed circuit board of claim 4, wherein the first via, the
second vias and the third vias are sized and positioned to provide
an impedance in the first signal launch region and the second
signal launch region of between 40.OMEGA. and 80.OMEGA..
6. The printed circuit board of claim 3, in combination with an RF
connector module, wherein: the RF connector module comprises: a
lead frame providing a coplanar waveguide structure, the lead frame
comprising: a signal conductor, the signal conductor comprising a
contact tail; and a plurality of ground conductors disposed
adjacent the signal conductor, the plurality of ground conductors
comprising a plurality of contact tails; and at least one shield
member parallel to the lead frame; the contact tail of the signal
conductor is connected to the first via; and each of the plurality
of contact tails of the plurality of ground conductors is connected
to a second via.
Description
RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Application Ser. No. 61/666,674,
entitled "LOW COST, HIGH PERFORMANCE RF CONNECTOR" filed on Jun.
29, 2012, which is herein incorporated by reference in its
entirety.
BACKGROUND
[0002] The present disclosure relates generally to electrical
interconnections for connecting printed circuit boards ("PCBs") and
more specifically to interconnection systems for carrying RF
signals between printed circuit boards.
[0003] Electrical connectors are used in many electronic systems.
It is generally easier and more cost effective to manufacture a
system on several PCBs that are connected to one another by
electrical connectors than to manufacture a system as a single
assembly. A traditional arrangement for interconnecting several
PCBs is to have one PCB serve as a backplane. Other PCBs, which are
called daughter boards or daughter cards, are then connected
through the backplane by electrical connectors.
[0004] Connectors in different formats are used, depending on the
types or orientations of PCBs to be connected. Some connectors are
right angle connectors, meaning that they are used to join two
printed circuit boards that are mounted in an electronic system at
a right angle to one another. Another type of connector is called a
mezzanine connector. Such a connector is used to connect printed
circuit boards that are parallel to one another.
[0005] Examples of mezzanine connectors may be found in: U.S.
patent application Ser. No. 12/612,510, published as
US-2011-0104948-A1; International Application No.
PCT/US2009/005275, published as International Publication No.
WO/2010/039188; U.S. Pat. No. 6,152,747; and U.S. Pat. No.
6,641,410. All of these patents and patent applications are
assigned to the assignee of the present application and are hereby
incorporated by reference in their entireties.
[0006] Electronic systems have generally become smaller, faster and
functionally more complex. These changes mean that the number of
circuits in a given area of an electronic system, along with the
data rates, sometimes measured as bits per second or as a
frequency, at which the circuits operate, have increased
significantly in recent years. Current systems pass more data
between printed circuit boards and require electrical connectors
that are electrically capable of handling more data at higher
speeds than connectors of even a few years ago.
[0007] One of the difficulties in making a high density, high speed
data connector is that electrical conductors in the connector can
be so close that there can be electrical interference between
adjacent signal conductors. To reduce interference, and to
otherwise provide desirable electrical properties, metal members
are often placed between or around adjacent signal conductors. The
metal acts as a shield to prevent signals carried on one conductor
from creating "crosstalk" on another conductor. The metal also
impacts the impedance of each conductor, which can further
contribute to desirable electrical properties.
[0008] As data rates increase, there is a greater possibility of
electrical noise being generated in the connector in forms such as
reflections, crosstalk and electromagnetic radiation. Therefore,
the electrical connectors are designed to limit crosstalk between
different signal paths and to control the characteristic impedance
of each signal path. Shield members are often placed adjacent the
signal conductors for this purpose.
[0009] Crosstalk between different signal paths through a connector
can be limited by arranging the various signal paths so that they
are spaced further from each other and nearer to a shield, such as
a grounded plate. Thus, the different signal paths tend to
electromagnetically couple more to the shield and less with each
other. For a given level of crosstalk, the signal paths can be
placed closer together when sufficient electromagnetic coupling to
the ground conductors is maintained.
[0010] Although shields for isolating conductors from one another
are typically made from metal components, U.S. Pat. No. 6,709,294,
which is assigned to the same assignee as the present application
and is hereby incorporated by reference in its entirety, describes
making an extension of a shield plate in a connector from
conductive plastic.
[0011] In some connectors, shielding is provided by conductive
members shaped and positioned specifically to provide shielding.
These conductive members are designed to be connected to a
reference potential, or ground, when mounted on a printed circuit
board. Such connectors are said to have a dedicated ground
system.
[0012] In some connectors, designed for high frequency signals,
each signal conductor may be surrounded by shielding. This
configuration provides an electrical configuration similar to what
occurs in a coaxial cable in which a center conductor, carrying a
signal, runs through a tubular grounded sleeve, and is sometimes
referred to as a coaxial configuration. An example of such a
connector may be found in U.S. patent application Ser. No.
13/170,616 which is an example of a board to board connector with a
coaxial structure.
[0013] Other techniques may be used to control the performance of a
connector. For example, transmitting data signals differentially
can also reduce crosstalk. Differential signals are carried by a
pair of conducting paths, called a "differential pair." The voltage
difference between the conductive paths represents the signal. In
general, a differential pair is designed with preferential coupling
between the conducting paths of the pair. For example, the two
conducting paths of a differential pair may be arranged to run
closer to each other than to adjacent signal paths in the
connector. Conventionally, no shielding is desired between the
conducting paths of the pair, but shielding may be used between
differential pairs.
[0014] Examples of differential electrical connectors are shown in
U.S. Pat. No. 6,293,827, U.S. Pat. No. 6,503,103, U.S. Pat. No.
6,776,659, and U.S. Pat. No. 7,163,421, all of which are assigned
to the assignee of the present application and are hereby
incorporated by reference in their entireties.
[0015] Electrical characteristics of a connector also may be
controlled through the use of absorptive material. U.S. Pat. No.
6,786,771, which is assigned to the same assignee as the present
application and which is hereby incorporated by reference in its
entirety, describes the use of absorptive material to reduce
unwanted resonances and improve connector performance, particularly
at high speeds (for example, signal frequencies of 1 GHz or
greater, particularly above 3 GHz). U.S. Pat. No. 7,371,117, U.S.
Pat. No. 7,581,990, and U.S. patent application Ser. No.
13/029,052, published as US-2011-0230095-A1, which are assigned to
the assignee of the present application and are hereby incorporated
by reference in their entireties, describe the use of lossy
material to improve connector performance.
[0016] Modern systems sometimes operate based on RF signals. RF
signals might carry information representing video to be displayed
or might carry information to an antenna for wireless transmission.
Regardless of what information is carried by such a signal, passing
RF signals through an interconnection system joining printed
circuit boards can be challenging. The RF signals generally
represent information in analog form, such that any distortion of
the signal degrades the content of the information in the signal.
In contrast, for a digital data signal, which at any given time
represents a 1 or 0, so long as the noise or other distortion
introduced into the signal is not so significant that it precludes
a receiver from properly classifying the signal as a 1 or a 0, the
noise has relatively little impact. The same amount of noise on an
RF signal, however, might lead to perceptible distortion is the
audio or video quality of the signal when it is rendered for a
person or cause other undesired effects in a system using the RF
signal.
[0017] To preserve the quality of an analog RF signal, it is known
to make connectors to join printed circuit board to emulate a
coaxial structure. Such connectors may be made of machined metal
parts to provide a conductive ground structure surrounding a signal
conductor throughout each RF signal path in the interconnection
system.
SUMMARY
[0018] Aspects of the present disclosure relate to an improved, low
cost, RF connector, which may be used as a substitute for a coaxial
board-to-board connector. Such a connector may be provided using a
connector module with a co-planar waveguide structure in the
interior of the module. Dimensions of the elements of the co-planar
waveguide may be established to provide a desired impedance,
including for example 50.OMEGA. or 75.OMEGA. as is conventionally
provided by an RF coax connector. Though, controlling impedance by
varying dimensions of the co-planar waveguide allows impedance of
the connector module to be customized without impacting design of
other components such that a connector manufacturer may be able to
provide a variety of RF connectors of many different
impedances.
[0019] One or more construction techniques may be used to provide a
high isolation between RF signal conductors in the connector
module. Shielding may be provided at a peripheral portion of the
module, spacing the shields sufficiently far from the signal
conductors to provide minimal coupling of signal to the shields,
which would otherwise increase cross-talk between RF signal
conductors. Electrically lossy material may be incorporated to
suppress parallel plate modes and enforce even mode propagation
within the module.
[0020] Such a connector module may be simply and inexpensively
manufactured using one or more manufacturing techniques, such as:
stamping a lead frame to form the co-planar waveguide; embedding
the lead frame in an insultative housing; adding lossy material to
the insultative housing; and attaching planar shields to exterior
surfaces of the module.
[0021] Such techniques may be used alone or in combination to
achieve a connector module that provides in excess of 90 dB of
isolation between signals at frequencies in excess of 5 GHz. A
connector module with these characteristics may be used as a
replacement for a conventional RF coaxial connector in many
electronic assemblies.
[0022] Such a connector module may be attached to a printed circuit
board with a footprint adapted to provide high isolation between
signal conductors. The footprint may be formed using conventional
printed circuit board manufacturing techniques, allowing for a low
cost, though high performance, electronic assembly. The footprint
may provide for relatively high isolation between RF signal
conductors, even if those signal conductors are routed on the same
layer of a printed circuit board.
[0023] In other aspects, a two-piece connector may be provided with
signal conductors that have similar, but inverted shapes configured
to reduce stub length and improve performance of the connector. In
some embodiments, a signal conductor may have a mating contact
portion with a distal end with a planar portion and a beam portion.
The signal conductors may be oriented such that the beam portion of
a mating contact in one connector piece mates with the planar
portion of the mating contact in the other connector piece. This
arrangement provides multiple points of contact along the mating
contact portion.
[0024] Other advantages and novel features will become apparent
from the following detailed description of various non-limiting
embodiments of the present disclosure when considered in
conjunction with the accompanying figures and from the claims.
Accordingly, the claims should not be limited by the foregoing
summary.
BRIEF DESCRIPTION OF DRAWINGS
[0025] The accompanying drawings are not intended to be drawn to
scale. For purposes of clarity, not every component may be labeled
in every drawing.
[0026] FIG. 1 is a perspective view of a first connector suitable
for carrying data signals in an interconnection system in
combination with an RF connector as described herein;
[0027] FIGS. 2A and 2B are left and right side perspective views,
respectively, of an exemplary embodiment of a right angle RF
connector module mated with a corresponding backplane RF connector
module;
[0028] FIG. 3A is a left side perspective view of the right angle
RF connector module of FIGS. 2A and 2B;
[0029] FIG. 3B is a perspective view, from the mating interface
end, of the right angle RF connector module of FIGS. 2A and 2B;
[0030] FIGS. 4A and 4B are perspective views of the corresponding
backplane RF connector module of FIGS. 2A and 2B;
[0031] FIG. 5 is a left side, partially cut away perspective view
of the right angle RF connector module of FIGS. 2A and 2B, with the
insulative housing cut away to reveal conductive elements and lossy
regions within the connector module;
[0032] FIG. 6 is a partially cutaway perspective view of the
corresponding backplane RF connector module of FIGS. 2A and 2B,
with insulative portions cutaway to reveal conductive elements
within the corresponding connector module;
[0033] FIG. 7 is a perspective view of conductive elements of the
right angle RF connector of FIGS. 2A and 2B shown engaging mating
conductive elements of the corresponding connector module of FIGS.
2A and 2B;
[0034] FIGS. 8A, 8B and 8C are cross-sectional illustrations of
alternative embodiments of the meeting contact portions of the
conductive elements illustrated in FIG. 7;
[0035] FIG. 9A is a view, from the left side, of a right side
shield member of the RF connector module of FIGS. 2A and 2B
engaging a shield member of the corresponding backplane RF
connector module of FIGS. 2A and 2B;
[0036] FIG. 9B is an enlarged view, viewed from the right side, of
the right side shield members of FIG. 9A;
[0037] FIG. 10 is a plan view of the left side of the right angle
RF connector module and the corresponding connector module of FIGS.
2A and 2B;
[0038] FIG. 11 is a cross-sectional view along the line 4-4 in FIG.
10;
[0039] FIG. 12 is a cross-sectional view along the line 2-2 in FIG.
10;
[0040] FIG. 13 is a cross-sectional view along the line 1-1 in FIG.
10;
[0041] FIG. 14A is a cross-sectional view of conductive elements in
an RF connector module with a coplanar waveguide configuration;
[0042] FIG. 14B is a cross-sectional view of the RF connector
module of FIG. 14A showing electromagnetic fields associated with
propagating RF signals;
[0043] FIG. 14C is a cross-sectional view of conductive elements in
an RF connector module with a coplanar waveguide configuration, as
in FIG. 14A but with different dimensions, and showing
electromagnetic fields associated with propagating RF signals;
[0044] FIG. 15A is a cross-sectional view of conductive elements in
an RF connector as in FIG. 14A and with lossy regions, and showing
electromagnetic fields associated with propagating RF signals;
[0045] FIG. 15B is a cross-sectional view of conductive elements,
lossy regions and electromagnetic fields associated with
propagating RF signals in an RF connector module as in FIG. 15A,
but with different dimensions;
[0046] FIG. 16 is a plan view of a signal launch regions for RF
signals adapted for attachment of a connector module as in FIGS. 2A
and 2B; and
[0047] FIG. 17 is a plan view of an alternative embodiment of the
signal launch regions of FIG. 16, with tuning for RF signals.
DETAILED DESCRIPTION
[0048] The inventors have recognized and appreciated ways to
combine known manufacturing techniques to manufacture a low cost,
high performance interconnection system that carries RF signals.
The system may be manufactured using one or more connector modules
adapted for carrying RF signals. The RF connector modules may be
manufactured using techniques compatible with those used for
manufacturing high speed data connectors. However, the RF connector
modules may carry signals at RF frequencies with very high
isolation. As a specific example, a connector module as described
herein may provide greater than 90 dB of isolation between RF
signal conductors at 5 GHz.
[0049] In some embodiments, a connector module may be manufactured
using stamping and molding techniques as are known in the art for
manufacture of high speed data connectors. These operations may be
low cost in comparison to screw turning and other techniques known
in the art for making a coaxial connector. As in a data connector,
a lead frame with conductive elements may be stamped from a sheet
of metal, resulting in conductive elements arranged in a column.
However, for an RF connector, the conductive elements may be
stamped to provide conductive elements that carry RF signals.
[0050] Conductive elements providing ground conductors may be
stamped adjacent these signal conductors. The stamping may provide
for a single signal conductor between adjacent ground conductors,
supporting single-ended RF signal paths. Any number of such signal
paths may be provided in a lead frame. In some embodiments, for
example, two RF signal paths may be provided in a lead frame.
[0051] In some embodiments, the lead frame may be stamped to
provide for a co-planar waveguide structure. In such a structure,
signal conductors are positioned adjacent ground conductors. An RF
signal may propagate along the signal conductor as an
electromagnetic field primarily concentrated between the signal
conductor and adjacent ground conductors. Accordingly, dimensions
of the signal conductor and spacing relative to adjacent ground
conductors may primarily determine the impedance of the signal
conductor at RF frequencies.
[0052] The lead frame may be held within a support structure,
referred to herein as a housing. The housing may be partially or
totally insultative.
[0053] In some embodiments, planar conductive members or shield
members of other shapes may also be supported by the housing. The
shield members also may be stamped from a sheet of metal. They may
be attached to an exterior portion of the housing or incorporated
into the module in any suitable way. In some embodiments, there may
be more than one planar conductive member per module, and the
manner conductive members may be collectively configured to provide
shielding between RF signal conductors, whether in the same module
or, when multiple modules are used, adjacent modules.
[0054] In some embodiments, the shield members may be spaced
sufficiently far from the lead frame that the presence or shape of
the shield members does not significantly impact the impedance of
the RF signal conductor.
[0055] The housing, in addition to supporting the lead frame, may
support regions of lossy material. The lossy material may be
positioned within the housing to enforce propagation of the signal
in accordance with the co-planar structure. The lossy material, for
example, may be positioned to suppress undesired modes of
propagation. In structures with multiple conductors, these
structure may support multiple modes of electromagnetic energy. The
number of modes supported in a structure relates on the number of
conductors, such that there are n-1 modes of propagation for n
conductors. In the case of connector with a signal conductor and
two ground conductors, there are three conductors, so two modes of
propagation. The lossy material may be positioned to dampen the
mode that has lesser contribution to energy transmitted through the
connector or, conversely, causes greater interference on other
conductors. For two signal conductors and three ground conductors,
there are four modes supported. Lossy material may be positioned to
dampen one or more of these modes. In some embodiments, the TEM
mode of propagation may be desired such that the lossy material is
positioned to suppress non-TEM modes.
[0056] As another example, the lossy material also may be
positioned to suppress parallel plate modes of propagation between
the lead frame and the shield members. Such a structure may be
simply manufactured by inserting lossy regions into the
housing.
[0057] Shield members may then be attached to exterior surfaces of
the housing. In some embodiments, the shield members may be
electrically coupled through the lossy regions. Both mechanical
attachment and electrical coupling may be provided by pressing the
shield members against the surface such that the lossy regions
extend through openings in the shield members. Mechanical
attachment may be achieved by sizing the openings relative to the
lossy regions such that an interference fit is created. In some
embodiments, the lossy material may also contact the ground
conductors of the lead frame, tying together the grounded
conductive elements within the connector module.
[0058] Performance of an interconnection system incorporating such
an RF connector module may be enhanced through the use of printed
circuit boards that are adapted for use with the connector modules.
Such a printed circuit board, for example, may have multiple
layers, but may be configured to have traces carrying RF signals to
the signal conductors of the RF connector module on a single layer
of the printed circuit board. Moreover, the printed circuit board
may be configured so as to tune the impedance of the signal launch
where the RF connector module is mounted to the printed circuit
board. Alternatively or additionally, the printed circuit board may
be configured to provide isolation between the RF signal traces,
such as through the use of micro vias.
[0059] In some embodiments, the RF connector modules manufactured
as described herein may be physically sized for use with connector
modules carrying data signals. FIG. 1 provides an example of an
interconnection system using known data connectors into which RF
connector modules may be incorporated.
[0060] FIG. 1 shows an illustrative electrical interconnection
system 100 having two data connectors. In this example, the
electrical interconnection system 100 includes a daughter card
connector 120 and a backplane connector 150 adapted to mate with
each other to create electrically conducting paths between a
backplane 160 and a daughter card 140. Though not expressly shown,
the interconnection system 100 may interconnect multiple daughter
cards having similar daughter card connectors that mate to similar
backplane connectors on the backplane 160. Accordingly, aspects of
the present disclosure are not limited to any particular number or
types of subassemblies connected through an interconnection system.
Furthermore, although the illustrative daughter card connector 120
and the illustrative backplane connector 150 form a right-angle
connector, it should be appreciated that aspects of the present
disclosure are not limited to the use of right-angle connectors. In
other embodiments, an electrical interconnection system may include
other types and combinations of connectors, as the inventive
concepts disclosed herein may be broadly applied in many types of
electrical connectors, including, but not limited to, right angle
connectors, mezzanine connectors, card edge connectors, cable
connectors and chip sockets.
[0061] In the example shown in FIG. 1, the backplane connector 150
and the daughter connector 120 each contain conductive elements.
The conductive elements of the daughter card connector 120 may be
coupled to traces (of which a trace 142 is numbered), ground
planes, and/or other conductive elements within the daughter card
140. The traces may carry electrical signals, while the ground
planes may provide reference levels for components on the daughter
card 140. Such a ground plane may have a voltage that is at earth
ground, or positive or negative with respect to earth ground, as
any voltage level maybe used as a reference level.
[0062] Similarly, conductive elements in the backplane connector
150 may be coupled to traces (of which trace 162 is numbered),
ground planes, and/or other conductive elements within the
backplane 160. When the daughter card connector 120 and the
backplane connector 150 mate, the conductive elements in the two
connectors complete electrically conducting paths between the
conductive elements within the backplane 160 and the daughter card
140.
[0063] In the example of FIG. 1, the backplane connector 150
includes a backplane shroud 158 and a plurality of conductive
elements that extend through a floor 514 of the backplane shroud
158 with portions both above and below the floor 514. The portions
of the conductive elements that extend above the floor 514 form
mating contacts, shown collectively as mating contact portions 154,
which are adapted to mate with corresponding conductive elements of
the daughter card connector 120. In the illustrated embodiment, the
mating contacts portions 154 are in the form of blades, although
other suitable contact configurations may also be employed, as
aspects of the present disclosure are not limited in this
regard.
[0064] The portions of the conductive elements that extend below
the floor 514 form contact tails, shown collectively as contact
tails 156, which are adapted to be attached to backplane 160. In
the example shown in FIG. 1, the contact tails 156 are in the form
of press fit, "eye of the needle," compliant sections that fit
within via holes, shown collectively as via holes 164, on the
backplane 160. However, other configurations may also be suitable,
including, but not limited to, surface mount elements, spring
contacts, and solderable pins, as aspects of the present disclosure
are not limited in this regard.
[0065] In the embodiment illustrated in FIG. 1, the daughter card
connector 120 includes a plurality of wafers 122.sub.1, 122.sub.1,
. . . 122.sub.6 coupled together, each wafer having a housing
(e.g., a housing 123.sub.1 of the wafer 122.sub.1) and a column of
conductive elements disposed within the housing. Some conductive
elements in the column may be adapted for use as signal conductors,
while some other conductive elements may be adapted for use as
ground conductors. The ground conductors may be employed to reduce
crosstalk between signal conductors or to otherwise control one or
more electrical properties of the connector.
[0066] In the illustrated embodiment, the daughter card connector
120 is a right angle connector and has conductive elements that
traverse a right angle. As a result, opposing ends of the
conductive elements extend from perpendicular edges of the wafers
122.sub.1, 122.sub.1, . . . 122.sub.6. For example, contact tails
of the conductive elements of the wafers 122.sub.1, 122.sub.1, . .
. 122.sub.6, shown collectively as contact tails 126, extend from
side edges of the wafers 122.sub.1, 122.sub.1, . . . 122.sub.6 and
are adapted to be connected to the daughter card 140. Opposite from
the contact tails 126, mating contacts of the conductive elements,
shown collectively as mating contact portions 124, extend from
bottom edges of the wafers 122.sub.1, 122.sub.1, . . . 122.sub.6
and are adapted to be connected corresponding conductive elements
in the backplane connector 150. Each conductive element also has an
intermediate portion between the mating contact portion and the
contact tail, which may be enclosed by or embedded within the
housing of the wafer (e.g., the housing 123.sub.1 of the wafer
1220.
[0067] The contact tails 126 may be adapted to electrically connect
the conductive elements within the daughter card connector 120 to
conductive elements (e.g., the trace 142) in the daughter card 140.
In the embodiment illustrated in FIG. 1, contact tails 126 are
press fit, "eye of the needle" contacts adapted to make an
electrical connection through via holes in the daughter card 140.
However, any suitable attachment mechanism may be used instead of,
or in addition to, via holes and press fit contact tails.
[0068] In the example illustrated in FIG. 1, each of the mating
contact portions 124 has a dual beam structure configured to mate
with a corresponding one of the mating contact portions 154 of the
backplane connector 150. However, it should be appreciated that
aspects of the present disclosure are not limited to the use of
dual beam structures. For example, some or all of the mating
contact portions 124 may have a triple beam structure. Other types
of structures, such as single beam structures, may also be
suitable. Furthermore, a mating contact portion may have a wavy
shape adapted to improve one or more electrical and/or mechanical
properties and thereby improve the quality of a signal coupled
through the mating contact portion.
[0069] In the example of FIG. 1, some conductive elements of the
daughter card connector 120 are intended for use as signal
conductors, while some other conductive elements of the daughter
card connector 120 are intended for use as ground conductors. The
signal conductors may be grouped in pairs that are separated by the
ground conductors, in a configuration suitable for carrying
differential signals. Such pairs may be designated as "differential
pairs", as understood by one of skill in the art. For example,
though other uses of the conductive elements may be possible, a
differential pair may be identified based on preferential coupling
between the conductive elements that make up the pair. Electrical
characteristics of a pair of conductive elements, such as
impedance, that make the pair suitable for carrying differential
signals may provide an alternative or additional method of
identifying the pair as a differential pair. Furthermore, in a
connector with differential pairs, ground conductors may be
identified by their positions relative to the differential pairs.
In other instances, ground conductors may be identified by shape
and/or electrical characteristics. For example, ground conductors
may be relatively wide to provide low inductance, which may be
desirable for providing a stable reference potential, but may
provide an impedance that is undesirable for carrying a high speed
signal.
[0070] While a connector with differential pairs is shown in FIG. 1
for purposes of illustration, it should be appreciated that
embodiments are possible for single-ended use in which conductive
elements are evenly spaced without designated ground conductors
separating designated differential pairs, or with designated ground
conductors between adjacent designated signal conductors.
[0071] In the embodiment illustrated in FIG. 1, the daughter card
connector 120 includes six wafers 122.sub.1, 122.sub.1, . . .
122.sub.6, each of which has a plurality of pairs of signal
conductors and a plurality ground conductors arranged in a column
in an alternating fashion. Each of the wafers 122.sub.1, 122.sub.2,
. . . 122.sub.6 is inserted into a front housing 130 such that the
mating contact portions 124 are inserted into and held within
openings in the front housing 130. The openings in the front
housing 130 are positioned so as to allow the mating contact
portions 154 of the backplane connector 150 to enter the openings
in the front housing 130 and make electrical connections with the
mating contact portions 124 when the daughter card connector 120 is
mated with the backplane connector 150.
[0072] In some embodiments, the daughter card connector 120 may
include a support member instead of, or in addition to, the front
housing 130 to hold the wafers 122.sub.1, 122.sub.2, . . .
122.sub.6. In the embodiment shown in FIG. 1, a stiffener 128 is
used to support the wafers 122.sub.1, 122.sub.2, . . . 122.sub.6.
The stiffener 128 may be made of stamped metal, or any other
suitable material, and may be stamped with slots, holes, grooves
and/or any other features for engaging a plurality of wafers to
support the wafers in a desired orientation. However, it should be
appreciated that aspects of the present disclosure are not limited
to the use of a stiffener. Furthermore, although the stiffener 128
in the example of FIG. 1 is attached to upper and side portions of
the plurality of wafers, aspects of the present disclosure are not
limited to this particular configuration, as other suitable
configurations may also be employed.
[0073] In some further embodiments, each of the wafers 122.sub.1,
122.sub.2, . . . 122.sub.6 may include one or more features for
engaging the stiffener 128. Such features may function to attach
the wafers 122.sub.1, 122.sub.2, . . . 122.sub.6 to the stiffener
128, to locate the wafers with respect to one another, and/or to
prevent rotation of the wafers. For instance, a wafer may include
an attachment feature in the form of a protruding portion adapted
to be inserted into a corresponding slot, hole, or groove formed in
the stiffener 128. Other types of attachment features may also be
suitable, as aspects of the present disclosure are not limited in
this regard.
[0074] In the embodiment illustrated, the wafers, when inserted
into front housing 130 form a connector module. Such connector
module is adapted for carrying high-speed data signals. When
attached to stiffener 128, such a connector module may form a
portion of an overall connector. That connector may include other
modules adapted for carrying high-speed data signals. Alternatively
or additionally, the connector may include other types of modules
attached to stiffener 128, including an RF connector module.
[0075] FIGS. 2A and 2B illustrate a right angle RF connector module
210 that is sized for attachment to stiffener 128. In the
configuration shown, RF connector module 210 is shown mated to a
corresponding backplane RF connector module 250. In use, RF
connector module 210 may be mounted to stiffener 128 adjacent other
like RF connector modules, adjacent data connector modules as
illustrated in FIG. 1 or connector modules of other types.
Similarly, backplane RF connector module 250 may be attached to
backplane 160 adjacent backplane module 150 or other suitable type
of backplane module. Though, it should be appreciated that the RF
connector modules as described herein may be used as part of a
connector with or without high-speed data connector modules.
[0076] FIG. 2A is a left side, perspective view of a right angle,
RF connector module 210 mated with backplane RF connector module
250. FIG. 2B is a right side, perspective view of RF connector
module 210 and backplane RF connector module 250. As with the
high-speed data connector illustrated in FIG. 1, right angle, RF
connector module 210 includes an insulative housing 220.
[0077] In this example, housing 220 has exterior dimensions and
features conforming to those of the high-speed data connector of
FIG. 1 such that RF connector module 210 may be mounted to
stiffener 128 along with high-speed data connector modules. Though,
RF connector module 210 may have a different width (in a direction
along stiffener 128) than the connector module illustrated in FIG.
1. The width of RF connector module 210 may be selected to
approximate an integer multiple of the width of the wafers in FIG.
1. Such a width may facilitate attaching one or more RF connector
modules to stiffener 128, but is not a requirement of the
invention.
[0078] Housing 220 may be made of any suitable material. Suitable
materials include insulative materials known in the art for use in
forming electrical connector housings. The material may be
thermoplastic to facilitate forming housing 220 using a molding
operation. In the embodiment illustrated, housing 220 is molded
from a dielectric material such as plastic or nylon. Examples of
suitable materials are liquid crystal polymer (LCP), polyphenyline
sulfide (PPS), high temperature nylon or polypropylene (PPO). Other
suitable materials may be employed, as the present invention is not
limited in this regard. All of these may be suitable for use as
binder materials in manufacturing connectors according to some
embodiments of the invention. One or more fillers may be included
in some or all of the binder material used to form housing 220 to
control the mechanical properties of housing 220. For example,
thermoplastic PPS filled to 30% by volume with glass fiber may be
used to form housing 220. Fillers to control the electrical
properties of regions of the backplane connector may also be
used.
[0079] Regardless of the material used to form housing 220,
conductive elements may be positioned within housing 220. The
conductive elements may be shaped to act as RF signal conductors
and/or ground conductors. The signal and ground conductors may be
sized and positioned relative to each other to provide a desired
impedance for RF signals passing through RF connector module
210.
[0080] In the view shown in FIG. 2A, intermediate portions of the
conductive elements within housing 220 are not visible. However,
contact tails extending from the intermediate portions of the
conductive elements within housing 220 are visible. Contact tails
224A and 224B are contact tails for RF signal conductors. Contact
tails 222A, 222B . . . 222H are contact tails for ground
conductors.
[0081] Any suitable technique may be used to manufacture RF
connector module 210 with intermediate portions of the conductive
elements within housing 220. An example of a suitable techniques is
insert molding. In accordance with such a technique, the conductive
elements may be stamped from a sheet of metal as a single lead
frame, which may include tie bars and carrier strips that hold the
conductive elements together for handling as a single component.
Insulative material forming housing 220 may then be molded around
the lead frame using insert molding techniques as are known in the
art. Once the conductive elements of the lead frame are held with
in the housing 220, the conductive elements may be separated from
carrier strips or other supporting portions of the lead frame.
Though, the specific technique for incorporating conductive
elements within housing 220 is not critical to the invention. In
some embodiments, for example, housing 220 may be formed in
multiple pieces. The conductive elements may then be placed within
or attached to one of the pieces. The pieces of the housing may be
attached to each other, leaving the conductive elements within the
housing.
[0082] FIGS. 2A and 2B illustrate other elements that may be
included in right angle, RF connector module 210. FIG. 2A shows a
shield member 230A attached to a left side of RF connector module
210. FIG. 2B shows a shield member 230B attached to a right side of
connector module 210. In this example, shield members 230A and 230B
have generally planar shapes. Accordingly, each of the shield
members 230A and 230B may be attached to a surface of insulative
housing 220.
[0083] Any suitable attachment technique may be used to attach
shield members 230A and 230B to insulative housing 220. In the
example illustrated in FIGS. 2A and 2B, mechanical attachment of
the shield members is achieved by an interference fit between the
shield members and portions of the housing extending above the
outer surface to which the shield members are attached. Those
extending regions may be partially or totally conductive such that,
in addition to a mechanical attachment, electrical connections to
the shield members may be formed.
[0084] FIGS. 2A and 2B show lossy regions 240A, 240B . . . 240E.
Portions of those lossy regions extend above the outer surface of
insulative housing 220. The extending portions align with openings
in the shield members 230A and 230B. Those extending portions of
the lossy regions may have dimensions slightly larger than the
dimensions of openings in the shield members. Accordingly, when the
shield members are pressed against the surface, the lossy regions
240A, 240B . . . 240E may be deformed to pass through the openings.
The portions of the lossy regions that pass through the openings
may expand, capturing the shield plates against the surfaces of
insultative housing 220.
[0085] The lossy regions 240A, 240B . . . 240E may be formed in any
suitable way. An example of a suitable manufacturing techniques is
a molding operation. In some embodiments, RF connector module 210
may be formed using a multi-shot molding operation, such as a two
shot molding operation. In a first shot, insulative housing 220 may
be insert molded around the lead frame. The mold used for the first
shot may have features providing openings for lossy regions 240A,
240B . . . 240E. For the second shot, these features may be
removed, and voids left by removing those features may be filled
with lossy material, creating a lossy region that extends above the
surface of insulative housing 220. Though, any suitable
manufacturing technique may be used.
[0086] FIGS. 2A and 2B illustrate opposing sides of RF connector
module 210. As can be seen in these views, lossy regions 240A, 240B
. . . 240E extend through insulative housing 220. Both shield
members 230A and 230B are mechanically attached to lossy regions
240A, 240B . . . 240E. In this way, the shield members may be
electrically coupled through the lossy regions.
[0087] Any suitable lossy material may be used to form lossy
regions 240A, 240B . . . 240E. Materials that conduct, but with
some loss, over the frequency range of interest are referred to
herein generally as "lossy" materials. Electrically lossy materials
can be formed from lossy dielectric and/or lossy conductive
materials. The frequency range of interest depends on the operating
parameters of the system in which such a connector is used, such as
up to 25 GHz, though higher frequencies or lower frequencies may be
of interest in some applications. Some connector designs may have
frequency ranges of interest that span only a portion of this
range, such as 1 to 10 GHz or 3 to 15 GHz or 3 to 6 GHz.
[0088] Electrically lossy material can be formed from material
traditionally regarded as dielectric materials, such as those that
have an electric loss tangent greater than approximately 0.003 in
the frequency range of interest. The "electric loss tangent" is the
ratio of the imaginary part to the real part of the complex
electrical permittivity of the material. Electrically lossy
materials can also be formed from materials that are generally
thought of as conductors, but are either relatively poor conductors
over the frequency range of interest, contain particles or regions
that are sufficiently dispersed that they do not provide high
conductivity or otherwise are prepared with properties that lead to
a relatively weak bulk conductivity over the frequency range of
interest. Electrically lossy materials typically have a
conductivity of about 1 siemens/meter to about 6.1.times.10.sup.7
siemens/meter, preferably about 1 siemens/meter to about
1.times.10.sup.7 siemens/meter and most preferably about 1
siemens/meter to about 30,000 siemens/meter. In some embodiments
material with a bulk conductivity of between about 10 siemens/meter
and about 100 siemens/meter may be used. As a specific example,
material with a conductivity of about 50 siemens/meter may be used.
Though, it should be appreciated that the conductivity of the
material may be selected empirically or through electrical
simulation using known simulation tools to determine a suitable
conductivity that provides both a suitably low cross talk with a
suitably low insertion loss.
[0089] Electrically lossy materials may be partially conductive
materials, such as those that have a surface resistivity between 1
.OMEGA./square and 106 .OMEGA./square. In some embodiments, the
electrically lossy material has a surface resistivity between 1
.OMEGA./square and 10.sup.3 .OMEGA./square. In some embodiments,
the electrically lossy material has a surface resistivity between
10.OMEGA./square and 100 .OMEGA./square. As a specific example, the
material may have a surface resistivity of between about 20
.OMEGA./square and 40 .OMEGA./square.
[0090] In some embodiments, electrically lossy material is formed
by adding to a binder a filler that contains conductive particles.
Examples of conductive particles that may be used as a filler to
form an electrically lossy material include carbon or graphite
formed as fibers, flakes or other particles. Metal in the form of
powder, flakes, fibers or other particles may also be used to
provide suitable electrically lossy properties. Alternatively,
combinations of fillers may be used. For example, metal plated
carbon particles may be used. Silver and nickel are suitable metal
plating for fibers. Coated particles may be used alone or in
combination with other fillers, such as carbon flake. The binder or
matrix may be any material that will set, cure or can otherwise be
used to position the filler material. In some embodiments, the
binder may be a thermoplastic material such as is traditionally
used in the manufacture of electrical connectors to facilitate the
molding of the electrically lossy material into the desired shapes
and locations as part of the manufacture of the electrical
connector. Examples of such materials include LCP and nylon.
However, many alternative forms of binder materials may be used.
Curable materials, such as epoxies, can serve as a binder.
Alternatively, materials such as thermosetting resins or adhesives
may be used. Also, while the above described binder materials may
be used to create an electrically lossy material by forming a
binder around conducting particle fillers, the invention is not so
limited. For example, conducting particles may be impregnated into
a formed matrix material or may be coated onto a formed matrix
material, such as by applying a conductive coating to a plastic
housing. As used herein, the term "binder" encompasses a material
that encapsulates the filler, is impregnated with the filler or
otherwise serves as a substrate to hold the filler.
[0091] Preferably, the fillers will be present in a sufficient
volume percentage to allow conducting paths to be created from
particle to particle. For example, when metal fiber is used, the
fiber may be present in about 3% to 40% by volume. The amount of
filler may impact the conducting properties of the material.
[0092] Filled materials may be purchased commercially, such as
materials sold under the trade name Celestran.RTM. by Ticona. A
lossy material, such as lossy conductive carbon filled adhesive
preform, such as those sold by Techfilm of Billerica, Mass., US may
also be used. This preform can include an epoxy binder filled with
carbon particles. The binder surrounds carbon particles, which acts
as a reinforcement for the preform. Such a preform may be inserted
in a wafer to form all or part of the housing. In some embodiments,
the preform may adhere through the adhesive in the preform, which
may be cured in a heat treating process. In some embodiments, the
adhesive in the preform alternatively or additionally may be used
to secure one or more conductive elements, such as foil strips, to
the lossy material.
[0093] Various forms of reinforcing fiber, in woven or non-woven
form, coated or non-coated may be used. Non-woven carbon fiber is
one suitable material. Other suitable materials, such as custom
blends as sold by RTP Company, can be employed, as the present
invention is not limited in this respect.
[0094] As shown in FIGS. 2A and 2B, right angle RF connector module
210 mates with backplane RF connector module 250. In the embodiment
illustrated, backplane RF connector module 250 includes a shroud
260. Shroud 260 may be made of an insulative material, and may be
made of the same insulative material as housing 220. Shroud 260 may
be made in a molding operation, though any suitable construction
technique may be used. For example, in alternative embodiments,
some or all of shroud 260 may be made of conductive or partially
conductive material, including powdered metals. Though, if shroud
260 is conductive or partially conductive, signal conductors
passing through shroud 260 may be held in insulative material that
separates the signal conductors from shroud 260.
[0095] Mounted within shroud 260 are shield members 270A and 270B.
Shield member 270A is visible in FIG. 2A, showing the left side of
backplane RF connector module 250. Shield member 270 B is visible
in FIG. 2B, showing the right side of backplane RF connector module
250.
[0096] In the embodiment illustrated, shield members 270A and 270B
are planar conductive members. These members may be stamped from a
sheet of metal or formed in any other suitable way from conductive
material. Each of the shield members 270A and 270B may contain
contacts 272 adapted to make electrical contact with portions of
shield members 230A and 230B, respectively. The contacts may have
any suitable shape. In this example, the contacts 272 each contain
a compliant portion which, when right angle RF connector module 210
is mated with backplane RF connector module 250, press against a
respective shield member 230A or 230B. In this specific example of
FIGS. 2A and 2B, each of the shield members 270A and 270B has three
contacts 272. Each of the contacts 272 is of the same shape. This
shape is illustrated to provide a torsional beam type contact.
[0097] Each of the shield members 230A and 230B may have one or
more contact tails 274, adapted for making electrical contact with
a printed circuit board, such as backplane 160 (FIG. 1). In this
example, the contact tails are compliant, eye of the needle contact
tails, which may be used for a press fit attachment of backplane RF
connector module 250 to a printed circuit board. Though, any
suitable type of contact tail may be used.
[0098] Shield members 230A and 230B may be attached to shroud 260
in any suitable way. Each shield member, for example, may be
inserted in slots in opposing sidewalls of shroud 260. The contact
tails may pass through openings a floor of shroud 260.
[0099] Other shield members may alternatively or additionally be
inserted into shroud 260. FIGS. 2A and 2B show shield members 264.
As with other shield members, shield members 264 may be stamped of
metal or otherwise formed in whole or in part of a conductive
material. In this example, shield members 264 are perpendicular to
shield members 270A and 270B and also may be inserted into slots,
such as slot 262, in the floor of shroud 260.
[0100] Shield members 264 may be electrically coupled to shield
members 270A and 270B. In the example of FIGS. 2A and 2B, each of
the shield members 264 is electrically coupled to both shield
members 270A and 270B. This coupling may be provided in any
suitable way, including by providing openings in shield members
270A and 270B sized to receive shield members 264, but with a tight
enough fit that electrical contact is made.
[0101] Shield members 270A and 270B alternatively or additionally
may be shaped to make contact with shield members 264 when right
angle RF connector module 210 is mated with backplane RF connector
module 250. Each of the shield members 270A and 270B may contain
slots (364, FIG. 3A) that are positioned to align with shield
members 264. Such a configuration serves to tie together the
forward edges of shield members 270A and 270B.
[0102] Though not visible in FIGS. 2A and 2B, backplane RF
connector module 250 may contain conductive elements. These
conductive elements may be shaped to provide signal conductors and
ground conductors. The signal conductors and ground conductors of
backplane RF connector module 250 may align with corresponding
signal and ground conductors of right angle RF connector module
210. These signal conductors also may be formed in any suitable
way, including by stamping from a sheet of metal. The signal and
ground conductors may then be inserted into openings in the floor
of shroud 260.
[0103] FIGS. 3A and 3B show in further detail right angle RF
connector module 210. Here, right angle RF connector module 210 is
illustrated without backplane RF connector module 250. In this
configuration, two portions of shield member 230A are visible.
Portion 310A rests against a surface of insulative housing 220
(FIG. 2A). Portion 312A extends beyond the insulative housing.
Portion 312A extends into the mating interface area of RF connector
module 210.
[0104] In the embodiment illustrated, portions 310A and 312A of
shield member 230A are formed from a unitary sheet of metal. Though
shield member 230A is a generally planar shield member, a
transition 314A may be included between portions 310A and 312A.
Transition 314A allows the spacing between different portions of
shield members 230A and 230B to be different. In this example,
transition 314A brings the portions 312A and 312B closer together
at the mating interface area than over portions of insulative
housing 220.
[0105] In operation, portion 312A mates with shield member 270A of
backplane RF connector module 250 when the connector modules are
mated. Slots 364 are visible in the forward mating edge of portion
312A. Slots 364 may engage shield members 264 when the connector
modules are mated.
[0106] Shield member 230B may similarly have two portions. Portion
312B, like portion 312A, extends beyond insulative housing 220 into
a mating interface area. Though not visible in FIGS. 3A and 3B,
shield member 230B may also include a portion adjacent insulative
housing 220.
[0107] FIG. 3B reveals additional details of the mating interface
portion of RF connector module 210. A column 350 of conductive
elements extends from insulative housing 220 to form the mating
interface area. The extending portions may form mating contacts for
RF connector module 210. The mating contacts, in the embodiment
illustrated, are positioned between portions 312A and 312B of
shield members 230A and 230B, respectively.
[0108] The mating contact portions may have any suitable size and
shape. In an embodiment as illustrated in which each RF connector
module 210 is configured to carry two RF signals, two of the mating
contacts in column 350 may be the mating contact portions of RF
signal conductors within RF connector module 210. Others of the
mating contacts in column 350 may be the mating contact portions of
ground conductors. In this example, mating contacts 324A and 324B
may the mating contacts for RF signal conductors. The remaining
mating contacts, of which mating contacts 322A, 322B, 322D and 322E
are numbered, may be mating contacts for ground conductors.
[0109] Though the RF connector module 210 may be designed such that
the primary mode of propagation of an RF signal is within a
coplanar waveguide created within a lead frame embedded within
insulative housing 220, some energy may have the tendency to
propagate in other modes, which could create interference between
RF signals in an interconnection system. In the embodiment
illustrated, shield members 230A and 230B are parallel to column
350. In this configuration, the shield members may block RF
radiation from an RF signal conductor in one RF connector module
210 from causing interference with an RF signal on an RF signal
conductor in another nearby RF connector module.
[0110] Additionally, one or more features may be included in RF
connector module 210 to reduce interference between RF signal
conductors within column 350. These features additionally may
decrease the amount of radiation propagating from one RF connector
module to another. For example, shield members 230A and 230B also
may reduce interference along the column 350. As illustrated in
FIGS. 2A and 2B, in operation, the mating edges of shield members
230A and 230B may be coupled to ground through contacts 272, which
may reduce the amount of RF signal energy that propagates in a
direction along the column 350 or that radiates from shield members
230A and 230B to create interference in other RF connector
modules.
[0111] Alternatively or additionally, the shield members 230A and
230B may be electrically connected together through shield members
264 of backplane RF connector module 250. Such a configuration may
also reduce the amount of RF signal energy that propagates along
column 350 or that radiates from a shield members 230A and 230B.
Alternatively or additionally, inclusion of lossy regions, such as
lossy regions 240A . . . 240E (FIG. 2A) may reduce the amount of RF
signal energy that propagates along column 350 or that radiates
from shield members 230A and 230B. Electromagnetic energy near
shield members 230A and 230B may be at least partially dissipated
by the lossy regions connecting those shield members.
[0112] FIG. 3B illustrates yet a further feature that may be
included within RF connector module 210 to reduce the amount of RF
signal energy that propagates along column 350. In the embodiment
illustrated, tabs 370A and 370B extend from portions 312A and 312B,
respectively. Tabs 370A and 370B may be electrically connected to
other portions of shield members 230A and 230B such that those
portions may also be coupled to ground and to lossy material within
RF connector module 210.
[0113] Each of tabs 370A and 370B may be positioned along column
350 two fall between two RF signal conductors. In the embodiment
illustrated, tabs 370A and 370B are approximately halfway between
mating contact portions 324A and 324B of the RF signal conductors
in RF connector module 210. Alternatively or additionally, tabs
370A and 370B may be positioned to align with mating contact
portions of ground conductors. In this example, tabs 370A and 370B
extend perpendicular to column 350 at a location aligned with
mating contact 322C of a ground conductor within RF connector
module 210.
[0114] Tabs 370A and 370B may be manufactured in any suitable way.
In some embodiments, tabs 370A and 370B may be integrally formed
with portions 312A and 312B. For example, an opening, such as
opening 372A in portion 370A, may be stamped in the same sheet of
metal used to form a shield member. The material from the opening
may be bent to be perpendicular to the plane of the shield member.
Though, any suitable construction techniques may be used to form
tabs 370A and 370B.
[0115] Turning to FIGS. 4A and 4B, further details of backplane RF
connector module 250 are illustrated. FIGS. 4A and 4B reveal shroud
260, shield members 270A and 270B, as well as shield members 264.
Additionally, conductive elements within shroud 260 are visible. A
column 450 of conductive elements is positioned between shield
members 270A and 270B. Column 450 is positioned such that the
conductive elements in column 450 will mate with the conductive
elements in column 350 when a right angle RF connector module 210
is mated with a backplane RF connector module 250.
[0116] In FIGS. 4A and 4B, signal conductors 424A and 424B and
ground conductors 422B and 422C of column 450 are numbered. These
conductive elements may be of any suitable shape. In this example,
signal conductors 424A and 424B have the same shape, which is a
different shape than ground conductors 422B and 422C.
[0117] The elements of backplane RF connector module 250 may be
formed and assembled in any suitable way, including using materials
and techniques as are known in the art in the manufacture of
high-speed data connectors. For example, shroud 260 may be molded
of an insulative material, which may be the same material used to
form housing 220 (FIG. 2A). Though, in some embodiments, portions
of shroud 260 may be formed of a lossy material. In yet other
embodiments, shroud 260 may be formed of metal or other conductive
material. In those embodiments, insulated spacers may be used to
separate signal conductors 424A and 424B from shroud 260.
[0118] Shroud 260 may be formed with features that facilitate
attachment of other elements that form backplane RF connector
module 250. As shown, shroud 260 may be formed with a floor 412 and
sidewalls 414. Floor 412 may have openings and/or slots adapted to
receive conductive elements. For example, floor 412 may be molded
with slots, each of which has a shape to receive a shield member
264. As shown, there are multiple shield members 264. Accordingly,
there may be multiple such slots in floor 412.
[0119] Sidewalls 414 may have features to which other elements of
RF backplane connector module 250 are attached. For example,
channels 410 are shown in sidewalls 414. Each of the channels 410
receives one end of a shield member 270A or 270B.
[0120] Some or all of the conductive elements within backplane RF
connector module 250 may be attached to a printed circuit board,
such as backplane 160, or other substrate to which connector module
250 is attached. Such connections may be made through contact tails
274 extending through a lower surface of floor 412. Contact tails
extending from shield members 270A or 270B, for example, may extend
through floor 412. Similarly, some or all of the conductive
elements in column 450 may have contact tails extending through
floor 412.
[0121] Though not included in the illustrated embodiment, shield
members 264 also may have contact tails. Rather, in the illustrated
embodiment, shields 264 are coupled indirectly to a printed circuit
board. In this specific example, shield members 264 are connected
to shield members 270A and 270B. Additionally, shield members 264
are connected to ground conductors, such as ground conductors 422B
or 422C.
[0122] Turning to FIG. 5, further details of the construction of
right angle RF connector module 210 are provided. FIG. 5 shows
connector module 210 with insulative housing 220 cut away. In this
view, shield members 230A and 230B are visible. Between shield
members 230A and 230B, lead frame 530 is positioned. In this
example, lead frame 530 is equidistant from shields 230A and
230B.
[0123] From this perspective, lossy regions, of which lossy regions
240B and 240E are numbered, are visible. In this configuration, the
lossy regions extend from one surface to an opposing surface of
right angle RF connector module 210. Those lossy regions extend
through the surfaces such that a projecting portion, of which
projecting portion 542E of lossy region 240E is numbered. These
projecting portions may be used to form an electrical connection
between the lossy regions and shield members 230 A and 230B on the
exterior of module 210. The projecting portions also may be used
for mechanical attachment of the shield members 230A and 230B to
those surfaces.
[0124] In this example, an interference fit between shield member
230A and projecting portion 542E is used to mechanically attach
shield member 230A to RF connector module 210. That interference
fit may be created using a hole in shield member 230A. In this
specific example, a hole is formed with a slightly conical rim
540E. To attach shield member 230A, the shield member may be
pressed against the surface of module 210, forcing projecting
portion 542E through the hole. In this example, the periphery of
the hole defined by rim 540E is slightly smaller than the periphery
of projecting portion 542E. Because, in the embodiment illustrated,
lossy region 240E is formed from a material having a plastic
binder, projecting portion 542E will deform sufficiently to pass
through the hole. The conical shape of rim 540E allows shield
member 230A to move relatively easily toward the insulative housing
of connector module 210, but will dig into projecting portion 542E,
preventing shield member 230A from being moved away from the
insulative housing.
[0125] The same form of attachment may be used for each of the
lossy regions 240A . . . 240E, providing both electrical and
mechanical connections across each of the shield members 230A and
230B. A similar form of attachment may be used to hold shield
member 230B to an opposing side of right angle RF connector module
210.
[0126] FIG. 5 also reveals a signal launch region 510B where an RF
signal may pass between right angle RF connector module 210 and a
printed circuit board to which connector module 210 is attached.
That signal launch region includes contact tails from lead frame
530 and contact tails extending from shield members 230A and 230B.
Here, signal launch region 510B includes contact tail 224B,
extending from an RF signal conductor in lead frame 530. Contact
tails 222F and 222G extending from ground conductors in lead frame
530 may also be included in signal launch region 510B. Further,
contact tails extending from shield members 230A and 230B may also
be included. The contact tails extending from the ground conductors
and shield members 230A and 230B may be connected together in the
printed circuit board, such as by a common ground plane.
[0127] In this way, contact tail 224B of the RF signal conductor
may be surrounded, in a generally circular pattern, by contact
tails attached to ground. The diameter of this circle may be
selected to provide a desired impedance for the signal launch
region. The diameter may be controlled by adjusting parameters,
including: spacing of the contact tails within lead frame 530;
spacing of the contact tails on shield members 230A and 230B; and
the separation between contact tail 224B of the RF signal conductor
and portions 530A and 530B of shield members 230A and 230B. In the
illustrated embodiment, portions 530A and 530B are formed as
extensions from portions 310A and 310B of shield members 230A and
230B. Accordingly, the separation between portions 310A and 310B
may be different than the separation between portions 310A and
310B. In this example, transitions between portions 310A and 310B
and portions 530A and 530B, respectively, position portions 530A
and 530B closer together than portions 310A and 310B.
[0128] A similar signal launch region may be formed around other
signal conductors within RF connector module 210. A signal launch
region 510A is shown around another RF signal conductor in module
210. In modules containing more than two signal conductors,
additional signal launch regions may be present.
[0129] Turning to FIG. 6, additional details of backplane RF
connector module 250 are shown. FIG. 6 illustrates backplane RF
connector module 250 with shroud 260 cut away. In this view, shield
members 270A and 270B as well as shield members 264 are visible.
Each of the shield members 264 is coupled near each end to one of
the shield members 270A and 270B, electrically connecting shield
members 270A and 270B at multiple locations. Conductive elements in
column 450 are also visible. Ground conductors 422A, 422B and 422C
are shown.
[0130] In this embodiment, column 450 also contains two RF signal
conductors 424A and 424B. These conductive elements are configured
such that each of the RF signal conductors 424A and 424B is
positioned between, and is adjacent to, two ground conductors. For
example, RF signal conductor 424A is positioned between adjacent
ground conductors 422A and 422B. RF signal conductor 424B is
positioned between adjacent ground conductors 422B and 422C. In
this way, a coplanar waveguide is formed around each of the signal
conductors within backplane connector module 250.
[0131] Column 450 is here positioned equidistant from shield
members 270A and 270B. Though, equidistant spacing from the shield
members is not a requirement. In some embodiments, column 450 may
be positioned closer to one of shield members 270A and 270B than
the other. The spacing to the nearer shield member may be selected
to provide a desired impedance to RF signal conductors 424A and
424B. Positioning RF signal conductors 424A and 424B closer to a
shield member, for example, may decrease the impedance of the
signal conductor. Though, the same effect on impedance may be
achieved by reducing the spacing between shield members 270A and
270B. However, in the embodiment illustrated, column 450 is
separated from shield members 270A and 270B by a sufficient
distance that the impedance of the RF signal conductors is
determined primarily by the spacing between the RF signal
conductors 424A and 424B and adjacent ground conductors 422A, 422B
and 422C of the coplanar waveguides.
[0132] FIG. 7 shows further detail of an RF connector assembly. In
FIG. 7, lead frame 530 of right angle RF connector module 210 is
shown mated with the conductive elements of column 450 of backplane
RF connector module 250. In this example in which two RF signal
conductors are included within the connector modules, two narrow
conductive elements 724A and 724B act as RF signal conductors. Each
of the conductive elements 724A and 724B is adjacent, on two sides,
to wider conductive elements 722A, 722B or 722C. In operation,
conductive elements 722A, 722B or 722C may act as ground conductors
by virtue of connection to a conductive structure connected to a
ground in the interconnection system.
[0133] The dimensions of lead frame 530 may be selected to provide
a desired impedance. Though, as noted above, other parameters, such
as spacing relative to shields 230A and 230B may, in some
embodiments, influence impedance. The width of conductive elements
724A and 724B as well as the edge to edge spacing to adjacent
conductive elements 722A, 722B or 722C may be selected to provide a
desired impedance. For RF connectors, the selected impedance may be
50 Ohms or 75 Ohms to match the impedance of conventional coaxial
connectors. However, there is no requirement that these
conventional impedance values be met. To the contrary, the
construction for an RF connector illustrated in FIG. 7 may be
readily adapted to any desired impedance by changing the lead frame
530 and the corresponding column 450 of conductive elements in the
backplane connector module. As a result, a connector manufacturer
may economically provide a line of RF connector products with
impedance values tailored for specific applications.
[0134] FIG. 7 reveals additional details of the construction that
may be included in lead frame 530. In this example, conductive
elements 722A, 722B or 722C each contains one or more openings
740A, 740B . . . 740E. These openings allow lossy regions 240A,
240B . . . 240E to pass through conductive elements 722A, 722B or
722C. Openings 740A, 740B . . . 740E support manufacture of right
angle RF connector module 210 using insert molding techniques. For
example, during a second shot molding operation, molten lossy
material may be inserted into openings in housing 220 that align
with openings 740A, 740B . . . 740E. In this way, lossy regions
extending from one surface of insulative housing 220 to an opposing
surface may be simply formed. Once formed in this way, the lossy
regions will be in contact with conductive elements 722A, 722B and
722C, providing a lossy coupling between the conductive elements
that form the ground system of right angle RF connector module 210.
In the example illustrated in which the lossy regions are used for
attaching external shield members 230A and 230B, this construction
technique provides lossy coupling between external shield members
230A and 230B and the conductive elements 722A, 722B and 722C
forming the ground portions of coplanar waveguides internal to
connector module 210.
[0135] FIG. 7 also reveals details of an exemplary mating interface
between a right angle RF connector module 210 and a backplane RF
connector module 260. In this example, the mating interface uses a
beam on pad configuration. The conductive elements of lead frame
530 each terminate in one or more beams, forming at least a portion
of the mating contact for the conductive element. Conductive
element 722A has, at a distal end, mating contact 322A. Conductive
element 722B, in this example, has three mating contacts 322B, 322C
and 322 D. Conductive element 722C has meeting contacts 322E and
322F. In this example, each of the mating contacts for the
conductive elements acting as ground conductors is shaped as a
beam. The dimensions of the beam may be selected to provide a
desired contact force, and may be selected as in a high-speed data
connector design or in any other suitable way.
[0136] The conductive elements in column 450 have mating contact
portions that are generally planar. The planar configuration of the
mating contacts of column 450 provides pads against which the beams
of the conductive elements in lead frame 530 may press for mating.
In the mated configuration illustrated in FIG. 7, mating contact
322A presses against a planar portion of conductive element 422A.
Mating contacts 322B, 322C and 322D, associated with conductive
element 722B, press against a planar portion of mating contact
422B. Similarly, mating contacts 322E and 322F press against a
planar portion of conductive element 422C.
[0137] The mating contacts of the signal conductors in right angle
RF connector module 210 similarly may be shaped to form beams
similar to those formed on the ground conductors. Though, in some
embodiments, the signal conductors may have mating contacts shaped
differently than those for the ground conductors. In some
embodiments, either or both of the mating contacts in right angle
RF connector module 210 and/or backplane RF connector module 250
may include at least two portions shaped and positioned to engage a
corresponding conductive element from the meeting connector module
at least two locations. In some embodiments, the two portions of a
mating contact may be configured to press against opposing sides of
the corresponding conductive element
[0138] In the embodiments illustrated in FIGS. 6 and 7, for
example, the mating contacts for each of the signal conductors may
contain both a beam portion and a planar portion. Such a
configuration of signal conductors 424A and 424B is visible in FIG.
6, with a beam 820 and a planar portion 822. Such a configuration
may improve the integrity of signals passing through the RF
connector modules. FIGS. 8A, 8B and 8C illustrate how such a
configuration for a mating contact improves signal integrity.
[0139] FIG. 8A shows a mating contact formed as a single beam 810
engaging a mating contact formed with a planar portion 812. Single
beam 810, for example, may represent a mating contact of a signal
conductor within right angle RF connector module 210. Planar
portion 812 may represent a mating contact of a signal conductor in
a backplane RF connector module 250. FIG. 8A illustrates that beam
810 makes contact with planar portion 812 a distance S.sub.1 from
the distal end of planar portion 812. This distance S.sub.1 creates
an un-terminated, conductive member attached to a signal path
through the mating contacts illustrated in FIG. 8A. Such a
conductive member is sometimes referred to as a "stub".
[0140] A stub can, under some conditions, cause signal reflections
or other distortions of a signal passing through the mating
contacts, degrading signal integrity. Specifically, a stub may
cause significant interference when the length S.sub.1 is an
appreciable fraction of the wavelength of signals propagating
through the mating contacts. As the frequency of the signal
increases, the wavelength decreases such that for an RF signal,
which has a relatively high frequency, what might appear as a
relatively short stub may cause significant signal disruptions.
[0141] FIG. 8B illustrates a side view of a mating contact formed
with a planar portion 822 and a beam 820. Planar portion 822 and
beam 820 are, in the configuration illustrated in FIG. 8B,
positioned side-by-side with their longitudinal axes in parallel.
In the view illustrated, a cross-section is taken through planar
portion 822, which is in front of beam 820.
[0142] The mating contact illustrated in FIG. 8B is an example of a
mating contact that can provide multiple points of contact that are
distributed longitudinally along an axis of the conductive
elements. When mated with a mating contact from a corresponding
connector, one point of contact can be formed on planar portion 822
and a second point of contact can be formed on beam 820. The mating
contact from the corresponding connector may be shaped such that
these points of contacts are offset in a direction along the length
of planar portion 822 and beam 820. In this configuration, multiple
points of contact can reduce the length of a stub formed at the
distal ends of the mating contacts.
[0143] FIG. 8C illustrates how multiple points of contact reduces
the length of a stub. In the embodiment illustrated in FIG. 8C, the
mating contact with the corresponding connector has the same shape
as the mating contact illustrated in FIG. 8B. However, the
orientation of the mating contact is reversed. FIG. 8B shows a beam
820A and a planar portion 822A that form the mating contact of a
conductive element of a connector, such as right angle RF connector
module 210. A second beam 820B and a second planar portion 822B
form the mating contact of a conductive element in a corresponding
connector, such as backplane RF connector module 250. In the
configuration illustrated in FIG. 8C, planar portion 822A is in
front of beam 828A, but beam 820B is in front of planar portion
822B.
[0144] With this configuration multiple points of contact along the
length of the meeting contact portion has the effect of reducing
the stub length to S.sub.2, which more closely approximates the
distance between the point of contact for a beam 820A or 820B and
the end of the beam.
[0145] Though, it should be appreciated that mating contacts of
other shapes may alternatively or additionally be used to reduce
the length of a stub formed when a mating contact engages a mating
contact from a corresponding connector.
[0146] FIGS. 8A, 8B and 8C represents mating contacts on signal
conductors. Similar mating contacts may be used on ground
conductors. However, in the embodiments illustrated in FIG. 7, the
mating contacts for ground conductors are different than those used
for the signal conductors. In FIG. 7, ground conductors within lead
frame 530 have mating contacts that are shaped as single beams
(though some of the conductive elements include multiple single
beam meeting contacts).
[0147] Other types of mating contacts may be used for shield
members in some embodiments. FIGS. 9A and 9B illustrate additional
details of the mating of external shield members. For simplicity,
FIGS. 9A and 9B illustrate an external shield member 230B from a
right angle RF connector module 210 engaging a shield number 270B
and shield members 264 from a backplane RF connector module
250.
[0148] Slots, such as slots 364 (FIG. 3A) in shield member 230B
engage shield members 264. The engagement between shield number
230B and shield members 264 may be formed in any suitable way. In
some embodiments, shield member 230B may be stamped with compliant
portions forming the sidewalls of slots 364 such that a tight fit
may be formed between shield member 230B and each of the shield
members 264. Though, in other embodiments, other coupling
mechanisms alternatively or additionally may be used. For example,
slots 364 may be sized to be slightly narrower than the width of
shield members 264 such that an interference fit is formed between
each slot 364 and a shield member 264. In yet other embodiments,
slots 364 may be sized to be slightly wider than the width of
shield members 264. This configuration may reduce the insertion
force for mating of right angle RF connector module 210 and
backplane RF connector module 250, but may provide less reliable
contact. However, for some embodiments, other points of contact
tying together conductive elements that are grounded may provide
sufficient coupling between the ground conductors of the connector
modules.
[0149] As shown in FIGS. 9A and 9B, shield members 264 are
electrically coupled to shield members, of which shield member 270B
is illustrated, in backplane RF connector module 250. Those shield
members are in turn coupled to the external shield members in the
right angle RF connector module 210. Coupling between shield member
230B and shield member 270B is provided through contacts 272.
[0150] A connection between shield members 264 and shield member
270B may be provided in any suitable way. As shown, each of the
shield members 264 is inserted into a slot with in shield member
270B. The slot may have walls shaped to provide compliant portions
that are deformed, and therefore generate contact force, when
shield members 264 are inserted in the slots. Alternatively,
coupling between shield members 264 and shield number 270B may be
formed as a result of an interference fit or loose placement of the
shield members in the slots, or in any other suitable way.
[0151] Contacts 272 may have any suitable configuration. However,
in the embodiment illustrated, contacts 272 are torsional contacts.
Such a contact is formed by stamping a beam from the same sheet of
metal used to form shield member 270B. The beam may remain attached
at both ends to the body of shield number 270B. That beam may be
twisted out of the plane of shield member 270B. In the
configuration shown in FIG. 9B, beams 272 are twisted out of the
plane of shield number 270B towards shield 230B. Upon the mating
between connector modules 210 and 250, shield member 230B will
press against beam 272, generating a torsional spring force in beam
272, which provides a contact force.
[0152] Regardless of the specific coupling mechanisms, the
connector modules, when mated, though cantilever beam shaped
contacts or contacts of any suitable shape may be used, provide RF
signal paths in which the electrical properties are dominated by a
coplanar waveguide structure. FIG. 10 illustrates, in plan view,
the right angle RF connector module 210 mated with backplane RF
connector module 250. In this figure, contact tails, of which
contact tails 274 and 224A and 224B are numbered, are shown. Such
contact tails may be used to attach, electrically and mechanically,
the connector modules to printed circuit boards in an
interconnection system. Though, for simplicity of illustration, the
printed circuit boards are not shown in FIG. 10.
[0153] The coplanar waveguide structure can be seen in cross
sections through the mated connector modules. FIG. 10 illustrates
cross sections 4-4 through the intermediate portions of the
conductive elements within right angle RF connector module 210.
Cross section 2-2 passes through the mating interface of the
connector modules. Cross section 1-1 passes through the mated
connector modules near the floor of backplane RF connector module
250.
[0154] FIG. 11 shows cross-section 4-4. In this view, two coplanar
waveguides are visible. Coplanar waveguide 1110A is formed around
conductor element 724A. Coplanar waveguide 1110B is formed around
conductive element 724B. In coplanar waveguide 1110A, signals
predominately propagate around conductive element 724A,
concentrated between conductive element 724A and adjacent
conductive elements 722A and 722B. In coplanar waveguide 1110B,
signals predominately propagate around conductive element 724B,
concentrated between conductive element 724B and adjacent
conductive elements 722B and 722C.
[0155] Shield members 230A and 230B prevent radiation from external
sources from interfering with propagation of RF signals along
conductive elements 724A and 724B. Those shield members also
prevent radiation from either of conductive elements 724A or 724B
from propagating to an adjacent conductive element.
[0156] Lossy regions, of which lossy regions 240A, 240 D and 240E
are illustrated in the cross-section of FIG. 11, also shape the
electromagnetic fields around conductive elements 724A and 724B to
reduce interference between each of the conductive elements
carrying a signal and adjacent signal conductors. Lossy regions
240D, for example, may damp any electromagnetic signal that might
otherwise tend to propagate across conductive element 722B.
[0157] Lossy region 240D, as well as other lossy regions such as
lossy regions 240A and 240E, provide lossy coupling between shield
members 230A and 230B. Rims 540A, 540D and 540E around openings in
shield member 230A are shown engaging lossy regions 240A, 240D and
240E, respectively. Similar rims (not numbered) around openings in
shield member 230B join shield 230B to the lossy regions.
[0158] FIG. 12 shows cross-section 2-2 through a mating interface
portion of the mated connector modules. Mating contact 322A from
connector module 210 is shown engaging conductive element 422A from
connector module 250. Other mating contacts from connector module
210, of which mating contact 322B is numbered, are shown engaging
conductive elements, of which conductive element 422B is numbered
from connector module 250. Mating contacts from connector module
210, of which mating contact 322F is numbered, are shown engaging
conductive element 422C from connector module 250.
[0159] Shield member 270B can be seen embedded in shroud 260.
Contact 272, which is bent out of the plane of shield 270B, makes
contact with shield member 230B. Similar contact is made between
shield member 270A and shield member 230A. Tabs 370A and 370B
extending from shield members 230A and 230B, respectively, are also
visible. Tabs 370A and 370B may, as illustrated in FIG. 12, be
positioned between adjacent signal conductors in a module, which
may tend to reduce interference between the signal conductors.
[0160] FIG. 13 shows a cross section 1-1 through the mated
connector modules. Cross section 1-1 passes through shroud 260.
Multiple shield members 264, here numbered 264A, 264B . . . 264I,
are visible. As can be seen, shield members 264A, 264B . . . 264I
span the distance between shield members 270A and 270B. Shield
members 264A, 264B . . . 264I are also in contact with shield
members 2308 and 230B. Moreover, shield members 264A, 264B . . .
264I are also in contact with the conductive elements of backplane
RF connector module 250 designated as ground conductors.
Specifically, shield member 264A makes electrical contact with the
conductive element 422A. Shield members 264D and 264E make
electrical contact with conductive element 422B. Shield members
264H and 264I make electrical contact with conductive element 422C.
With the conductive members forming ground conductors tied together
in this way, resonances and other adverse electrical effects within
the ground system are reduced.
[0161] The structure of the ground system may also provide a
transition to a connector footprint that avoids abrupt impudence
discontinuities, which may be undesirable for a connector carrying
RF signals. In the cross-section illustrated in FIG. 13, the
conductive elements 424A and 424B carrying RF signals do not have
the coplanar waveguide structure illustrated in FIG. 11. However,
conductive element 424A is surrounded by shield members 264B and
264C. Likewise, conductive element 424B is surrounded by shield
members 264F and 264G. As can be seen, shield member 264B is
approximately halfway between the edge of conductive element 424A
and a facing edge of conductive element 422A. Similarly, shield
member 264C is approximately halfway between an edge of conductive
element 424A and a facing edge of conductive element 422B.
[0162] This positioning of planar ground members tends to create
electromagnetic fields that approximate those that would exist in
the vicinity of conductive element 424A as part of a coplanar
waveguide structure. Though, the conductive structures serving as
ground conductors surrounding conductive element 424A in this
fashion more readily align with the conductive structures in a
printed circuit board to which a backplane RF connector module may
be attached. Examples of the conductive structures in a printed
circuit board are provided in FIGS. 16 and 17, below. Similar
alignment of conductive structures may be provided in signal launch
regions, such as region 510B, where connector module 210 is
attached to a printed circuit board.
[0163] FIGS. 14A, 14B and 14C illustrate parameters of a connector
design that may be varied to achieve a desired impedance and level
of isolation between signal conductors. FIG. 14A illustrates
schematically a cross-section similar to that shown in FIG. 11.
Signal conductors 1424A and 1424B are shown. Each of the signal
conductors 1424A and 1424B is shown between two adjacent ground
conductors 1422A, 1422B or 1422C. These conductive elements are
stamped from the same sheet of metal and have a thickness, T. The
signal conductors 1424A and 1424B have a width W, which in this
example is the same for both signal conductors.
[0164] Each of the signal conductors 1424A and 1424B has an edge to
edge spacing relative to an adjacent ground conductor of S.sub.3.
In this example, the edge to edge spacing for both edges of both
signal conductors is the same. However, it should be appreciated
that different signal conductors may have different edge to edge
spacing relative to an adjacent ground and different edges of the
same signal conductor may have different edge to edge spacing. The
specific values for the dimensions T, W and S.sub.3 may be selected
to provide a desired impedance, or other property, for RF signals
propagating along the signal conductors.
[0165] FIG. 14A shows that the conductive elements 1422A, 1424A,
1422B, 1424B, and 1422C are separated from adjacent shield members
1430A and 1430 be by a distance S.sub.4. In this example, the
distance relative to each shield member is the same. In other
embodiments, the distance may be different.
[0166] FIG. 14B illustrates the electromagnetic fields in the
vicinity of the signal conductors 1424A and 1424B when those signal
conductors are carrying RF signals. As can be seen, the
electromagnetic fields surrounding signal conductors 1424A and
1424B interact with shield members 1430A and 1430B. This condition
may allow electromagnetic radiation associated with an RF signal to
escape from shield members 1430A and 1430B, which may cause
interference with adjacent RF signal conductors. Additionally, this
configuration may allow propagation or resonance of electromagnetic
energy along or between shield members 1430A and 1430B, which may
reduce isolation between signal conductors 1424A and 1424B.
[0167] FIG. 14C illustrates that the amount of radiation
interacting with shield members 1430A and 1430B may be reduced by
increasing the distance S.sub.4. In the embodiment of FIG. 14 C,
that distance has been increased to distance S.sub.4'. As can be
seen by comparison of FIGS. 14B and 14C, a greater percentage of
the electromagnetic energy associated with the propagating RF
signal is concentrated between signal conductors 1424A and 1424B
with increased distance to distance S.sub.4'. Simultaneously, less
RF energy is available to interact with the shield members or to
otherwise cause interference between adjacent RF signal
conductors.
[0168] FIG. 15A illustrates a further technique that may be used to
reduce interference between adjacent RF signal conductors. FIG. 15A
illustrates the introduction of lossy regions 1440A, 1440B and
1440C into a connector module. As can be seen from a comparison of
FIGS. 14B and 15A, introduction of the lossy regions reduces the
amount of electromagnetic radiation associated with propagating RF
signals outside the regions between the RF signal conductors 1424A
or 1424B and the adjacent ground conductors forming the coplanar
waveguide structures. In the embodiment illustrated, the lossy
material is positioned to attenuate undesired modes of propagation,
thereby enforcing the desired mode of propagation. Thus, the effect
of introducing lossy material is to increase the percentage of the
RF signal energy carried within the coplanar waveguide structures.
For example, in some embodiments, greater than 85% of the signal
energy may propagate along the coplanar waveguide. In other
embodiments, this percentage may be 90%, 95% or 99% over a
frequency range of interest, such as 1-3 GHz.
[0169] FIG. 15B illustrates a further improvement that can be
achieved by both increasing the distance to distance S.sub.4' and
incorporating lossy regions. As a specific example, in some
embodiments, the distances:
[0170] T may be between 0.05 mm and 0.15 mm.
[0171] W may be between 0.2 mm and 0.45 mm.
[0172] S.sub.3 may be between 0.2 mm and 0.6 mm.
[0173] S.sub.4' may be 0.5 mm or greater.
[0174] Such dimensions may provide isolation between RF signals of
that is in excess of 75 dB and in some embodiments may be even
higher, such as in excess of 90 dB of isolation over a range of
frequencies in the RF range, such as 1 GHz to 3 GHz. Such a
connector may provide on impedance that is tunable, depending on
the specific dimensions selected. The impedance, for example, may
be tuned to be in the range of 40.OMEGA. to 80.OMEGA. at a
frequency in the range of 1-3 GHz. Though, in other embodiments,
the impedance may be tuned in the range of 45.OMEGA. to 55.OMEGA.
over the frequency range of 3 GHz to 6 GHz or 65.OMEGA. to
85.OMEGA. over the frequency range of 3 GHz to 6 GHz.
[0175] In addition to the design features for the connector modules
described above, other aspects of an interconnection system may
impact isolation between RF signal conductors or other performance
parameters. One such aspect is the technique used for mounting the
connector modules to printed circuit boards. A location of a
printed circuit board at which a connector is mounted is sometimes
called the connector "footprint". FIG. 16 illustrates a connector
footprint for a connector containing two RF modules described
above.
[0176] The footprint illustrated in FIG. 16 may be appropriate for
mounting two modules in the form of right angle RF signal module
210. In some embodiments, the connector modules may be manufactured
such that the same footprint may also be used for mounting modules
in the form of backplane RF connector module 250. Though, even if
the footprint for a backplane module 250 is not identical to that
used for mounting of a connector module 210, similar techniques may
be used to construct the footprint.
[0177] In this example, the connector footprint contains module
regions 1610A and 1610B. Each of the module regions is configured
for receiving contact tails from one connector module. In the
illustrated example, the contact tails are configured as press fit
contact tails and are inserted into plated vias. Accordingly, each
of the module regions 1610A and 1610B contains plated vias for
receiving contact tails from signal conductors and associated
ground conductors.
[0178] In the embodiments described above, each of the conductor
modules contains two RF signal conductors. Accordingly, each of the
module regions 1610A and 1610B contains two signal vias 1620A and
1620B, each adapted to receive a contact tail from an RF signal
conductor. Vias adapted to receive contact tails from associated
ground conductors may be positioned around each of vias 1620A and
1620B. Ground vias 1630A, 1632A, 1634A, 1636A, 1638A and 1640A are
shown positioned around signal via 1620A. Ground vias 1630B, 1632B,
1634B, 1636B, 1638B and 1640B are shown positioned around signal
via 1620B. Each signal via and associated ground vias may form a
signal launch for an RF signal and may receive contact tails from a
signal launch region, such as signal launch region 510B (FIG.
5).
[0179] As shown in FIG. 16, the ground vias are positioned
generally in a circle around the signal vias. The radius of this
circle may be selected to provide a desired impedance in the signal
launch. The impedance, for example, may approximate the impedance
for which the connector module is tuned.
[0180] The signal vias and ground vias may be constructed in any
suitable way, including using known printed circuit board
manufacturing techniques. Those techniques may include drilling a
hole through a printed circuit board and then plating the interior
walls of the hole with a conductive material. To form a signal via,
the whole may be drilled through a signal trace within the printed
circuit board on which the connector footprint is formed. If the
signal via passes through other layers of the printed circuit
board, any conductive material on those layers is positioned so
that the hole will not pass through the conductive material, unless
that conductive material is to be connected to the signal
trace.
[0181] To form a ground via, the via may be drilled through one or
more conductive layers within the printed circuit board that are
connected to ground. When the ground via is plated, connection to
ground is completed.
[0182] The diameters of the signal vias and ground vias may be
selected such that press fit contact tails will fit snugly within
the vias, making electrical and mechanical connections to the
plating on the interior portions of the vias. Additionally, micro
vias may be included in the connector footprint. Micro vias are
vias that have a smaller diameter than signal and ground vias. The
micro vias do not necessarily receive a contact tail. Rather, the
micro vias may be included to shape the electromagnetic fields in
the footprint.
[0183] FIG. 16 shows micro vias of which micro vias 1650 is
numbered. In the embodiment illustrated, the micro vias 1650 are
positioned in two parallel lines 1652 and 1654. Lines 1652 and 1654
of micro vias may reduce interference between RF signal conductors
within module regions 1610A and 1610B. In some embodiments, lines
1652 and 1654 of micro vias may align with shield members 230A and
230B, respectively, when connector module 210 is mounted at the
connector footprint.
[0184] Micro vias may also be arranged in a field 1656 between
signal vias in the same module region. Field 1656 of micro vias may
reduce interference between signal conductors in the same module
region.
[0185] In addition to providing a desired impedance and limiting
interference between signal conductors, the footprint illustrated
in FIG. 16 may accommodate single layer routing of RF signal traces
within a printed circuit board. FIG. 16 illustrates a signal trace
1660A connected to signal via 1620A. A signal trace 1660B is
connected to signal via 1620B. In constructing a printed circuit
board, the signal traces may run on an interior layer of the
printed circuit board. Though FIG. 16 may be regarded as
representing a surface of the printed circuit board, FIG. 16 also
may be regarded as representing any layer of the printed circuit
board, including a layer on which the signal traces are routed.
[0186] As can be seen in FIG. 16, the signal traces 1660A and 1660B
carrying RF signals to all of the connector modules can be routed
to the signal vias within the connector footprint without crossing
one another. Because crossing signal traces generally requires that
the traces be implemented on different layers of a printed circuit
board, routing all of the signal traces to the signal vias within
the connector footprint without crossing traces means that all of
the signal traces may be implemented on a single layer. In
conventional design of a printed circuit board that carries RF
signals, it is sometimes desirable for all the RF signal traces to
be implemented on a single layer, frequently an outermost layer of
the printed circuit board. Accordingly, the footprint illustrated
in FIG. 16 is compatible with conventional RF printed circuit board
design techniques.
[0187] Turning to FIG. 17, a variation of a connector footprint is
illustrated. The footprint of FIG. 17 includes RF signal launch
regions similar to those illustrated in connection with FIG. 16.
The footprint of FIG. 17 differs from the footprint of FIG. 16 in
that un-plated vias, such as un-plated vias 1770A, 1772A, 1774A or
1776A have been positioned around signal via 1720A. Similar
un-plated vias 1770B, 1772B, 1774B or 1776B may be positioned
around signal via 1720B. The number, size and/or position of the
un-plated vias may be selected to provide a desired impedance for
each RF signal launch. Such an approach may be useful in
embodiments in which other factors constrain positioning of
structures in the footprint that might yield a different impedance
than desired.
[0188] The ground vias in the connector footprint may align with
the contact tails, which may be positioned with a spacing driven by
the spacing between shield members. As a result, the configuration
of the signal launch region 510B on the connector module and the
configuration of the ground vias in the connector footprint may be
related such that positioning of the ground vias may be influenced
by parameters of the design of the connector module. Incorporating
un-plated vias in the connector footprint allows the impedance of
the signal launch to be adjusted to a desired value that might not
be achieved given the placement of the ground vias to receive
contact tails from the connector module.
[0189] In the embodiment illustrated in FIG. 17, four un-plated
vias are illustrated in the vicinity of each signal launch. For
example, un-plated vias 1770A, 1772A, 1774A and 1776A may be
positioned equidistant from signal via 1720A. The un-plated vias
1770A, 1772A, 1774A and 1776A in this example are between signal
via 1720A and ground vias 1730A, 1732A, 1734A, 1736A, 1738A and
1740A. Though, any suitable number and positioning of un-plated
vias may be used.
[0190] The un-plated vias may be made in any suitable way. As one
example, the un-plated vias may be formed by drilling holes through
the printed circuit board after plating of plated vias has been
performed. Though, in other embodiments, the un-plated vias may be
drilled before or as part of the same manufacturing operation as
the plated vias. The un-plated vias may then be temporarily or
permanently filled or coated with material that blocks the
conductive plating from adhering to the walls of the un-plated
vias. The un-plated vias, for example, may be filled with a
material of low dielectric constant relative to the material that
is used to form the matrix of the printed circuit board. This
material may remain in the un-plated vias or may be removed,
leaving air in the un-plated via, or removed and replaced with some
other material.
[0191] As an additional difference relative to the footprint of
FIG. 16, the footprint of FIG. 17 does not include field 1656 of
micro vias. FIG. 17 provides an example of a number and arrangement
of micro vias that may be appropriate in some embodiments. However,
it should be recognized that in other embodiments other numbers or
arrangements of micro vias may be used.
[0192] Various inventive concepts disclosed herein are not limited
in their applications to the details of construction and the
arrangements of components set forth in the following description
or illustrated in the drawings. The inventive concepts are capable
of other embodiments and of being practiced or of being carried out
in various ways. Also, the phraseology and terminology used herein
is for the purpose of description and should not be regarded as
limiting. The use of "including," "comprising," "having,"
"containing," or "involving," and variations thereof herein, is
meant to encompass the items listed thereafter and equivalents
thereof as well as additional items.
[0193] Having thus described several aspects of at least one
embodiment of the present disclosure, it is to be appreciated
various alterations, modifications, and improvements will readily
occur to those skilled in the art.
[0194] While examples of specific arrangements and configurations
are shown and discussed herein, it should be appreciated that such
examples are provided solely for purposes of illustration, as
various inventive concepts of the present disclosure are not
limited to any particular manner of implementation. For example,
aspects of the present disclosure are not limited to any particular
number of wafers in a connector, nor to any particular number or
arrangement of signal conductors and ground conductors in each
wafer of the connector.
[0195] As an example, coupling to lossy regions is described by way
of contact. In some embodiments, capacitive coupling or other forms
of indirect coupling may be used such that coupling is possible
even without direct or ohmic contact
[0196] Further, although many inventive aspects are shown and
described with reference to a right angle connector, it should be
appreciated that the present invention is not limited in this
regard, as the inventive concepts may be included in other types of
electrical connectors, such as mezzanine connectors, cable
connectors, stacking connectors, power connectors, flexible circuit
connectors, right angle connectors, or chip sockets.
[0197] As a further example, connectors with two RF signal
conductors in a column were used to illustrate the inventive
concepts. However, the connectors with any desired number of signal
conductors may be used.
[0198] Further, embodiments were illustrated in which connectors
may be mounted using press fit attachment techniques. To support
such attachment, the contact tails may be shaped as eye of the
needle contacts or otherwise contain compliant sections that can be
compressed upon insertion into a hole on a surface of a printed
circuit board. In other implementations, the contact tails may be
shaped to receive solder balls such that a connector may be mounted
to a printed surface board using known surface mount assembly
techniques. Other connector attachment mechanisms alternatively or
additionally may be used and contact tails of connectors may be
shaped to facilitate use of alternative attachment mechanisms. For
example, to support surface mount techniques in which component
leads are placed on solder paste deposited on the surface of a
printed circuit board, the contact tails may be shaped as pads. As
a further alternative, the contact tails may be shaped as posts
that engage holes on the surface of the printed circuit board.
[0199] In the embodiments illustrated, some conductive elements are
designated as forming signal conductors and some conductive
elements are designated as ground conductors. These designations
refer to the intended use of the conductive elements in an
interconnection system as they would be understood by one of skill
in the art. For example, though other uses of the conductive
elements may be possible, signal conductors may be identified based
on isolation from other like conductive elements. Electrical
characteristics of the signal conductors, such as its impedance,
that make it suitable for carrying a signal may provide an
alternative or additional method of identifying a signal conductor.
For example, a signal conductor may have an impedance of between 50
Ohms and 100 Ohms. As a specific example, a signal may have an
impedance of 50 or 100 Ohms+/-10%. As another example of
differences between signal and ground conductors, ground conductors
may be identified by their positioning relative to the signal
conductors. In other instances, ground conductors may be identified
by their shape or electrical characteristics. For example, ground
conductors may be relatively wide to provide low inductance, which
is desirable for providing a stable reference potential, but
provides an impedance that is undesirable for carrying a high speed
signal.
[0200] Further, though designated a ground conductor, it is not a
requirement that all, or even any, of the ground conductors be
connected to earth ground. In some embodiments, the conductive
elements designated as ground conductors may be used to carry power
signals or low frequency signals. For example, in an electronic
system, the ground conductors may be used to carry control signals
that switch at a relatively low frequency. In such an embodiment,
it may be desirable for the lossy member not to make direct
electrical connection with those ground conductors. The ground
conductors, for example, may be covered by the insulative portion
of a wafer adjacent the lossy member.
[0201] Further, lossy material is described as being positioned
such that it suppresses undesired modes of propagation.
Alternatively or additionally, the lossy material may be positioned
such that it increases the bandwidth of the connector.
[0202] Such alterations, modifications, and improvements are
intended to be part of this disclosure, and are intended to be
within the spirit and scope of the invention. Accordingly, the
foregoing description and drawings are by way of example only.
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